Its not reqd for vaccination but completing it speeds up the process if you dont have Nexus. Sort of like a fastrack

In terms of employee engagement and service levels on board, especially in J, my observation is that if the SD comes around and introduces themselves, the flight seems to be smooth and the service is good, procedures are followed. It's almost like they have ownership, and it shows as they set the standard. Individually, I have had great service from some FAs even if the SD is not engaged but rule of thumb is if the SD introduces, then it's going to be a good flight.
Overall, I do find the service on board has gotten better. On the ground it's been hit and miss, especially with the turnover around Covid. There have been some great concierges and some that really knew nothing. I don't know what AC does to engage with customers, especially their most loyal ones - feedback is easily sourced and most of us are not looking for a belly rub.
It seems the C-suite is looking at improving the experience, especially in premium. However, the execution and basics seem to slip thru the cracks - OTP, boarding process, IT self-help tools, etc.